What was scheduled to be a two-day negotiating session between the MTA and the Long Island Rail Road unions ended in less than four hours Thursday with no resolution, but with new proposals from both sides, officials said.

The MTA and the unions are now looking ahead to a likely second Presidential Emergency Board hearing this spring, in which White House-appointed mediators will again review both sides' best offers.

If no resolution is reached, some 5,800 LIRR workers could legally walk off the job July 19 -- stranding 300,000 daily commuters.

The National Mediation Board -- a quasi-independent agency formed under the Federal Railway Act to help resolve labor disputes -- invited the unions and the MTA to meet at its Washington, D.C., headquarters Thursday for what would have been the first round of negotiations since both sides squared off before presidential board mediators in December.

At the December session, the MTA rejected that board's recommendations for a 2.83 percent raise over six years and new health care contributions from LIRR workers. MTA officials have said the raises, without significant concessions, would require steep fare hikes, deferring important capital investments, or neglecting other financial obligations.

An MTA source who asked to remain anonymous said the agency's new offer Thursday was "hardly an acceptance" of the Presidential Emergency Board's recommendations, but rather an attempt to work within its constraints.

Anthony Simon, general chairman of the LIRR's largest labor organization, the Sheet Metal, Rail, Air and Transportation Union, said MTA officials, through the National Mediation Board, brought a new proposal Thursday under which the MTA would accept the presidential board's recommendations, with some changes.

Simon said the unions would not agree to those changes but sent the mediators back to the MTA with other proposed concessions.

Then, sometime before 3 p.m., the MTA contingent left the National Mediation Board offices, the union said.

"This was absolutely a disgrace. This was them coming here without any intention of making a deal," said Simon, who described the leaders of the eight represented unions as incensed. "You have two days to negotiate, and you walk out after three hours without getting in the same room with us."

But a source close to the MTA's negotiations said the agency representatives left only after mediators told them that the unions had gone to lunch and would return only if the MTA had a counter offer.

"We came in taking it seriously," MTA spokesman Adam Lisberg said. "I assume we would not have left without permission [from the NMB]."

Simon called Lisberg's version of the event a "bold-faced lie" and said the union representatives were in a conference room with their lunches when the MTA negotiators left.

The unions and the MTA headed back to New York Thursday without a deal.

A National Mediation Board spokesman declined to comment on what happened.

MTA chairman Thomas Prendergast disputed the unions' assertion that the authority was intentionally provoking a strike.

"I don't think labor, management, the public or elected officials want to get to an end game where there's a work stoppage or there's service not being provided," Prendergast said. "That's not in anyone's best interest."

THE ISSUES

The three net zeros.

The MTA is demanding that all its unions agree to a three-year freeze on total labor costs.

Raises.

A Presidential Emergency Board's recommendations, accepted by the unions, call for raises of 2.83 percent over six years. The MTA says any raises should be funded through union givebacks.

Impact on riders.

Without a freeze in labor costs, the MTA says it would have to raise fares by 12 percent next year, make deep cuts to service, or take $5 billion out of its next capital plan. Unions and the presidential board said the raises don't need to impact riders.

Work rules.

Among the concessions sought by the MTA is the abolishment of union work rules, including those paying conductors extra wages for certain assignments, double time and night differential. The presidential board did not recommend any work rule changes.

Health care and pension reform.

The MTA wants LIRR union workers, who currently pay nothing toward health care costs, to pay 12-14 percent of insurance premiums. The board recommended that workers pay 1 percent of health care costs, growing to 2.25 percent. The MTA also wants changes to LIRR pensions, including employee contributions and for pensions to be offset by the amount retirees receive in federal disability benefits. The board made no recommendations on pension reform.